1/8th Mile gearing - LS1TECH



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1/8th Mile gearing

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Old 03-10-2017, 07:30 PM   #1
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Default 1/8th Mile gearing

Most everything I read in this section is advice for 1/4 mile. I only have 1/8 mile tracks within a couple hours of me in any direction so that's the racing I'm gonna focus on. I have an 02 f body, 4l60e, 3500 lb race weight, on a 26" tire. 3.23 gears.

Currently run out of rpm at 6200 at the stripe. (We'll the tach shows 6200 and I know they're not really all that accurate). I either want to make it last to the 1/8th without a 2-3 shift or actually make use of 3rd if I shift into it.

Does anyone have any experience or recommendations? Don't mind a higher cruise rpm
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Old 03-10-2017, 07:45 PM   #2
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What do you trap in the 1/8 th and what torque converter are you running?

I have 3.73's 4l60e yank ss3600 which is around 6 % slip and second gets me to about 75 mph
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Old 03-10-2017, 07:46 PM   #3
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What torque converter? What times (a slip would help)?
Edit: Ha, same question @ same time....
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Old 03-11-2017, 11:30 AM   #4
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I don't have a big name converter like a yank or circle d. It's a custom stalled patc converter. Banging the Rev limiter in 2nd at the 1/8th I trap 84mph at around 8.30 et

1.85 60' on a 245/50r16 street tire. All at no prep events (most of what I run is a "hard tire" no prep class)
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Old 03-11-2017, 11:42 AM   #5
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Quote:
Originally Posted by MaroonMonsterLS1 View Post
I don't have a big name converter like a yank or circle d. It's a custom stalled patc converter. Banging the Rev limiter in 2nd at the 1/8th I trap 84mph at around 8.30 et

1.85 60' on a 245/50r16 street tire. All at no prep events (most of what I run is a "hard tire" no prep class)
To be able to get to the 1/8 in second gear you would need something like a 3.08 rear gear which should run you out to about 90 mph with 6 converter slip which is on the tighter side.
http://fitbodyshop.net/gear/index.php
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Old 03-11-2017, 12:36 PM   #6
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4.56...............
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Old 03-11-2017, 01:52 PM   #7
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if your running hard tire stuff and on a budget a slightly taller tire might be an option to consider. Taller tire will drop your rpm and let you hold 2nd and give you a longer contact patch to help with those 60 foot's.

Of course the other way to go will be a drastic gearing change like 01ssredA4 is suggesting , something like that 4.56/4.88 etc would be a more traditional 1/8 gear but you will then need to hook all that multiplied torque which is going to mean suspension upgrades so budget is a big factor in this decision also....
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Old 03-11-2017, 04:39 PM   #8
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I have tubular everything for rear suspension, competition engineering 3 way adjustable rear shocks. Only thing I haven't upgraded is the rear sway bar and the torque arm mount. I plan on moving it off the trans asap.

A taller tire sounds like a good idea, I'll have to look into what the tallest I can fit on a 8" wheel.
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Old 03-11-2017, 04:43 PM   #9
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Quote:
Originally Posted by MaroonMonsterLS1 View Post
I have tubular everything for rear suspension, competition engineering 3 way adjustable rear shocks. Only thing I haven't upgraded is the rear sway bar and the torque arm mount. I plan on moving it off the trans asap.

A taller tire sounds like a good idea, I'll have to look into what the tallest I can fit on a 8" wheel.
If you are trapping 84 mph a taller tire will slow you down
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Old 03-11-2017, 05:28 PM   #10
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Why is that? Taller tire at same rpm should be more mph?
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Old 03-11-2017, 06:57 PM   #11
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Quote:
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Why is that? Taller tire at same rpm should be more mph?
But you won't be at same rpm. I would do more gear and let it shift to 3rd.
Hell, I'm in third in the 1/8 (98mph), 3.42 gear 26" tire, and shifting at 6,700.
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Old 03-11-2017, 07:16 PM   #12
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My problem is I bang the limiter at the end. So if I could improve my 60' and avoid a 2-3 shift all at the same time that would be good. Even if I don't make limiter, that would still be fine as long as it doesn't hurt et
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Old 03-11-2017, 07:19 PM   #13
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Quote:
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Why is that? Taller tire at same rpm should be more mph?
Yup, but a lot slower out the hole if you don't have the power
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Old 03-11-2017, 07:21 PM   #14
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Slower out of the hole could be ok for me since I'm on a hard tire on an unprepped surface. If the loss up front will be paid off on the top end, I'm ok with that
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Old 03-12-2017, 08:02 AM   #15
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Two schools of thought. You are wanting to get there with less gear and more mph, I say get there with more gear and more rpm, make the 2/3 happen with an aggressive gear.
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Old 03-12-2017, 11:32 AM   #16
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if your going to change gear make it drastic so you get full benefit of that 3rd gear.

What about bumping the shift rpm for 2nd gear only just to get you to the traps ? bump it up 50rpm or so at a time until you just tick the limiter once or twice at the beams , I have done that with another platform (SC w body) where minor bolt on cars will need to shift 3rd in the 1/4 but can make the traps wringing out 2nd with a raised shift point for that gear only-no need to push your luck in every gear ...whats another 100 rpm lol
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Old 03-12-2017, 12:05 PM   #17
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Thats not a bad idea if its within a reasonable range.
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Old 03-13-2017, 01:50 PM   #18
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My engine is stock,I do too much travelling(about 185,000 currently) with it too start screwing around with the engine. I do test'n'tunes with the local group.
Back then I put in a TCI2800,was running 13.70s' before and after the convertor, convertor didn't change anything except provide excessive 'looseness'. Put in a 4.56 rearend,times changed from 13.70s' to 13.20s',1/8 time change dropped by .28 avg.
The TCI2800 was very loose at the top end. All racing was done in the 'auto' mode. 4th gear(overdrive) was required to get thru the 'traps'. With 4.10s',4th might have not been necessary.
With the 4.56s',I'd pull way ahead of 12 sec cars by half track and then they would go blowing by me at just past half track. Didn't have the power with the loose convertor to keep pulling.
I'm currently running a Yank SS3600 w 3.23s',haven't tracked the combo yet but it feels MUCH stronger with less slippage up top. Probably won't track the SS3600/3.23s' as when the weather breaks up here in northern Ohio,the 4.56 rearend is going back in. When that's in,I'll work on building a rearend with either 4.10s' or 3.73s'.
Before I removed the 4.56 rear and put in the 3.23 rear,I had the SS3600 in and some 'light to light' streetfighter action felt abnormally strong. 1st and 2nd were wicked.
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